Author Topic: Spotted denarii  (Read 1856 times)

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Offline Pellinore

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Spotted denarii
« on: February 09, 2016, 01:18:19 AM »
Here are three denarii, they haven't been touched for forty years. But the venerable emperors look like clowns, painted for children's games.
What can I do about this?

Can I use soap or washing-up liquid? Can I use microfibre?  How can I take off the dark staining?

-- Paul


Offline THCoins

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Re: Spotted denarii
« Reply #1 on: February 09, 2016, 08:48:25 AM »
You'd better not use any abbrasive method. I would start with dilluted lemon juice. If that is not enough then a short dilluted ammonia dip.
If that still not is sufficient aluminum foil might do the trick.

Anthony

Offline Pellinore

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Re: Spotted denarii
« Reply #2 on: February 09, 2016, 10:35:19 AM »
But lemon juice is acid, and I thought that's anathema for coins.
-- Paul

Offline THCoins

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Re: Spotted denarii
« Reply #3 on: February 09, 2016, 02:48:43 PM »
Acid + copper = BAD  :( 
Light Acid + Silver = handle with care  8)

Offline Figleaf

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Re: Spotted denarii
« Reply #4 on: February 09, 2016, 03:37:47 PM »
The coins are pretty good silver, but do you know what caused the spots? If it's moisture, light acid should indeed take care of it. If it's the storage vehicle (e.g. a coin cabinet made of young wood) you may want to try acetone.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline Pellinore

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Re: Spotted denarii
« Reply #5 on: February 09, 2016, 07:41:45 PM »
Good point. My father-in-law made a coin cabinet himself from triplex. The coins stayed in it for 40 years. Most have a darkish patina.
-- Paul

Offline Figleaf

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Re: Spotted denarii
« Reply #6 on: February 10, 2016, 07:51:22 AM »
With due respect for your father's abilities, which I cannot meet, as the name indicates, triplex consists of three layers, glued together under pressure. The glue will affect coins and with some bad luck, the sap in the young wood will be harmful also. You are lucky if you only kept silver and gold in that cabinet. A firm acetone treatment of its contents is called for.

Plastic coin cabinets (brand name SAFE) are relatively cheap, efficient, light and chemically stable and they can be ordered from the net. I wouldn't use their paper labels, though. Chloride in paper is now disallowed, but who needs the risk? You can easily create a "map" with details of each coin of each drawer with Excel. Otherwise, an antique (preferably oak) cabinet would be a good, but expensive replacement.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline bruce61813

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Re: Spotted denarii
« Reply #7 on: February 17, 2016, 11:38:35 PM »
You might try a commercial  non-abrasive silver cleaner, like "Dip-It". You literally dip the coin in for a few minutes and then buff with a soft cloth made for silver. If it is a silver sulfide stain, it may come out. The old method of putting the coin in baking soda wrap with aluminum foil and immerse in a vinegar/water bath, might also work.

Bruce

Offline Figleaf

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Re: Spotted denarii
« Reply #8 on: February 18, 2016, 09:28:24 AM »
Sadly, I have recent experience with dipping. The secret is in not overdoing it. Modern dips will no longer give the silver a steely look, but instead give it a nice, satiny finish. It works well on dirty coins, but rather than give them a 15 minutes bath, as it says on the label, I give them a maximum of 90 seconds, checking them every 30 seconds. I hold the coin with plastic pincers (came with an earlier pot o'dip). Also, I neutralise the dip with lukewarm water and dry thoroughly. If you are in a hurry, a hair dryer dries quickly and very well.

You can wipe off light discolouring with your fingers after dipping. However, dipping will not help against oxidation and hard chemical deposits and I think these coins have reacted with chemicals, rather than being polluted. With some luck, acetone will take care of many chemicals. Otherwise, you can fall back on the soft eraser method. However, this will destroy the patina.

Don't try any of the above on cu-ni, modern proofs, unc and ef coins with much original metal colour.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline Pellinore

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Re: Spotted denarii
« Reply #9 on: June 26, 2016, 11:02:20 PM »
Tonight I finally used acetone on the five denarii. It worked, not super, but well enough. There's some residue left on two of the coins. Result: a nice Titus Caesar with Neptune reverse, a nice Vespasian with caduceus, and an even better Trajan denarius. Plus two Trajans that are not good enough, for the swap tray.
-- Paul

Offline Figleaf

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Re: Spotted denarii
« Reply #10 on: June 29, 2016, 11:17:05 AM »
Very glad it worked for three of your coins. For the two Trajans, you may want to try Bruce's second recipe in reply #7.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline Pellinore

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Re: Spotted denarii
« Reply #11 on: July 11, 2016, 10:28:41 PM »
No, it's not that. They are F, not VF, that's the problem.

Offline Figleaf

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Re: Spotted denarii
« Reply #12 on: July 12, 2016, 11:15:33 AM »
As a last resort, try a soft eraser. It will destroy the patina, but patina will return in due time.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.